1. Field
Semiconductor packaging.
2. Description
Land Grid Array (LGA) packaging technology offers many advantages in terms of device manufacturing, high I/O density, low inductance, ease of upgrade, and cost.
An LGA socket is typically used to attach a LGA device such as a packaged chip to a printed circuit board (PCB). The typical loading required for LGA contact deflection generates lateral device (e.g., package) displacement driven by contact-to-device frictional forces. Package lateral displacement may continue until the device (e.g., package) comes in contact with the socket sidewall. Subsequently, frictional forces are generated between the device and the socket sidewall that can result in electrical opens or package damage through, for example, deformation to the device sidewalls or even breaking them.
Existing techniques to reduce the resultant friction force and moment during socket actuation have a number of drawbacks. Most LGA sockets or connectors have the LGA contacts wiping in one direction. While this configuration may be acceptable when the number of contacts is a few hundred, the resultant friction force and moment become significant when the number of contacts exceeds 1,000. Another technique lays out the LGA contacts into two diagonal triangular areas on a square socket with a square central cavity. However, when the socket or the central cavity is not square, some amount of moment results in reaction forces on the socket sidewall. In addition, the number of contacts in each row may be different in one area, causing complexities in manufacturing.